Thermal imaging devices allow an operator to see people and objects because they emit thermal energy. These imagers may be monoculars, binoculars, and goggles, whether hand-held, weapon mounted, or helmet mounted. These devices operate by capturing a portion of the infrared light spectrum, which is emitted as heat by objects or reflected by the objects instead of simply being reflected as visible light. Hotter objects, such as warm bodies, emit more of this wavelength than cooler objects like trees or buildings. Since the primary source of infrared radiation is heat or thermal radiation, any object that has a temperature radiates in the infrared. In addition, the reflectivity of an object may make it appear hotter or colder depending on the surrounding infrared sources and the emissivity of the object.